What is IFR?

By George Garza
Info Guru,

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Plane instrument panel
Instrument flight rules (IFR) are rules and procedures for flying aircraft where navigation and obstacle clearance is maintained using only aircraft instruments
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Why is flying by instrument important?

If you've wondered how pilots can fly at night or during a storm, the answer is that pilots use flying instruments. Flying involves two types of navigation: fly by sight and fly by instrument.


Pilot Rules and Procedures


Instrument flight rules (IFR) are rules and procedures for flying aircraft where navigation and obstacle clearance is maintained using only aircraft instruments. Thee separation from other aircraft is provided by air traffic control personnel.


VFR or visual flight rules are the alternative to IFR. With these rules the pilot is ultimately responsible for the flight including navigation, obstacle clearance and traffic separation using the see-and-avoid concept. The benefit of these regulations is that they allow an aircraft to safely fly through clouds, which is not permitted under VFR.


Stages of IFR Flight


In any IFR flight there are three stages: departure, en route and approach. For each stage there are standard, published guides and procedures to allow an IFR aircraft to move in a safe, orderly way.  


IFR Separation


All planes must maintain separation distance from other planes or obstacles at all times. This is the most important area of IFR flying. Separation is to be maintained regardless of weather or visibility conditions. In a controlled airspace the air traffic controllers separate flying aircraft from obstacles and other aircraft applying a flight clearance based on route, time, distance, speed and altitude differences among aircraft.


The air traffic controller system monitors IFR flights using either radar-positioning locators or aircraft-position reports. The aircraft-position reports are usually sent as voice-radio transmissions, but they are also sent as electronic data exchanges. However, aircraft position reports are not necessary if the air traffic control has an aircraft in radar contact. In the United States a flight operating under IFR is required to fall back to position reports if radar contact is lost.


IFR Clearance


Flight Rules require a clearance for each part of the flight. Each part of each flight has a specified clearance limit. So if you are going to fly by instrument, then you need to determine how far you can fly before you are required a new clearance level. Clearance is a distance limit. Other information such as the heading or route to follow, altitude and communication parameters are part of the clearance protocol.


In uncontrolled airspace IFR aircraft do not require clearances, and they separate themselves from one another by using charted minimum altitudes to avoid terrain and obstacles. They also use standard cruising altitudes to avoid aircraft flying in different directions. They file radio reports over mandatory locations.

IFR Airspace


Airspace from 18,000 to 60,000 feet (5,586 to 18,288 meters) is designated as class A airspace for the United States and Canada. This airspace is part of the IFR clearance for all aircraft. In the United States even if the pilot has filed an IFR flight plan, he is responsible to maintain a watch for and avoid other air traffic and obstructions if conditions permit.


What Traffic Is Controlled by IFR and VFR?


Most commercial traffic and all of the scheduled air carriers operate exclusively under IFR today. But commercial aircraft providing sightseeing flights, aerial photography or lift services for parachute jumping usually operate under VFR.


So What Is IFR?


It is a set of instrument flight rules that are used by pilots to enhance their visual flight experience. The rules help guide the pilots through airspace and assuring the public that safety rules are always in place during flight.

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